The blood clotting process consists of several of the most important types of reactions in protein chemistry, viz., enzymatic steps (proteolysis, transamidation, etc.) and protein association. In this project, we are concentrating on the proteolytic action of thrombin on fibrinogen. Synthetic work is being carried out to obtain oligopeptides that resemble the portion of the fibrinogen molecule that is attacked by thrombin. The kinetics of hydrolysis of the Arg-Gly bond, and the conformational properties of these oligopeptides are being studied. We thus hope to contribute to an understanding of the mechanism of this fundamental protein reaction, as it is involved in the blood clotting process, and, at the same time, to provide a basis for treating many of the cardio-vascular problems involving blood clotting (e.g., heart failure, stroke, hemophilia, etc.).